/Engine/Plugins/Animation/RigLogic/Source/RigLogicLib/Public/dna/layers/DefinitionReader.h
Requesting the parent index of joint 5 (joint name: F) would return 4 (joint name: E). Requesting the parent index of the root joint: 0 (joint name: A) would return the same index 0. An out of bounds request (an index greater than the number of joints returns UINT16_MAX).
std::uint16_t getJointParentIndex ( std::uint16_t index ) const